The Doctor Who Christmas Special has becoming a fun tradition for us. We get to it after all the important events and obligations are behind us. We can get back to our regular routine by way of a blue Police box.
A Christmas Carol felt very much like The Girl in the Fireplace. Both stories take place over a short period of time for the Doctor and for us, but for the people in the story or in this particular situation the Doctor's interventions took place over decades, over an entire lifetime. In this story, the Doctor takes a very active role in the character's history. A deliberate intervention to directly change the outcome or steer to the Doctor's desired possible future. This is a departure from the Doctor's usual modus operandi. It almost seemed like the Doctor's meddling could be seen as a punishment for the character in question's decision.
One interesting part that I expect will cause a lot of message board commotion is a character met himself and even embraced himself and there was no paradox.
It was a good addition to the list of adventures and the previews for season 6 look as cool as ever.